System and method for communicating between multiple voltage tiers

ABSTRACT

A system includes first, second, and third circuits and first and second capacitors. The first capacitor has a first power supply terminal coupled to positive power supply terminal, a second power supply terminal, and an input/output. The second capacitor has a first power supply terminal coupled the second power supply terminal of the first circuit, a second power supply terminal, and an input/output. The third circuit has a first power supply terminal coupled the second power supply terminal of the second circuit, a second power supply terminal, and an input/output. The first capacitor has a first terminal coupled to the input/output of the first circuit and a second terminal coupled to the input/output of the second circuit. The second capacitor has a first terminal coupled to the second terminal of the first capacitor and a second terminal coupled to the input/output of the third circuit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to a co-pending application Ser. No.12/621,005, By Perry Pelley, entitled “System Having Multiple VoltageTiers and Method Therefor”, and filed concurrently herewith.

BACKGROUND

1. Field

This disclosure relates generally to electronic circuits, and morespecifically, to a system and method for communicating between multiplevoltage tiers.

2. Related Art

Reducing power consumption in integrated circuits has become a highpriority. One way power is saved in logic circuits is to use multiplevoltage tiers to “stack” logic elements between power supply voltagerails. This allows a current used to perform one logic operation to bereused, or recycled, to perform additional logic operations. However, astransistor sizes are reduced, requiring lower power supply voltages,system noise becomes a larger percentage of the power supply voltage. Inthis case, the use of multiple voltage tiers becomes even moredifficult. Also, it may be necessary for circuits of the multiplevoltage tiers to be able to communicate with each other. One or morelevel shifters can be used to level shift a signal from one voltage tierto another, however, a level shifter can generally only translatebetween adjacent voltage tiers, requiring the use of multiple levelshifters when there are more than two voltage tiers.

Therefore, what is needed is a system that solves the above problems.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and is notlimited by the accompanying figures, in which like references indicatesimilar elements. Elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale.

FIG. 1 illustrates, in block diagram form, a system in accordance withan embodiment.

FIG. 2 illustrates, in block diagram form, a system in accordance withanother embodiment.

FIG. 3 illustrates, in block diagram form, a system in accordance withanother embodiment.

FIG. 4 illustrates, in block diagram form, an input/output (I/O) circuitif the circuit of FIG. 3.

DETAILED DESCRIPTION

Generally, there is provided, a plurality of circuits, where each of theplurality of circuits receives a power supply voltage that is apredetermined fraction of a rail-to-rail power supply voltage. A chargepump and regulator circuit is coupled to each of the power supplyterminals of each of the plurality of circuits. The charge pump andregulator circuit sinks or sources current at the power supply terminalsof one of the plurality of circuits to balance the amount of currentprovided through the circuit. Balancing the current provides for lesspower consumption while also providing for more reliable operation.Also, the use of multiple voltage tiers provides the benefits of a verylow power supply voltage while allowing the integrated circuit to bepowered using a more easily usable, customer friendly, power supplyvoltage.

Also, there is provided, a circuit for allowing communication betweencircuits of multiple voltage tiers. The circuit includes a plurality ofcapacitors coupled together in series, where a capacitor of the seriesis coupled between the outputs of input/output circuits corresponding toeach of the plurality of circuits. The series of capacitors are firstprecharged to a predetermined voltage. Then, when one of the I/Ocircuits provides a data bit to the series of capacitors, the data bitcauses the voltage stored on each capacitor to increase or decrease bythe same amount, thereby translating the data bit to each of thedifferent voltage tiers simultaneously. By translating the data bitusing the series of capacitors, level shifters are not required. Also,translating using the series of capacitors is much faster thantraditional level shifters because a traditional level shifter generallycan only level shift between adjacent voltage tiers. To level shift asignal between multiple voltage tiers requires a level shifter betweeneach tier and the level shifting between tiers must be done serially.

The integrated circuit may comprise a semiconductor substrate formedfrom any semiconductor material or combinations of materials, such asgallium arsenide, silicon germanium, silicon-on-insulator (SOI),silicon, monocrystalline silicon, the like, and combinations of theabove.

In one aspect, there is provided, a system, comprising: a first circuithaving a first power supply terminal coupled to positive power supplyterminal, a second power supply terminal, and an input/output; a secondcircuit having a first power supply terminal coupled the second powersupply terminal of the first circuit, a second power supply terminal,and an input/output; a third circuit having a first power supplyterminal coupled the second power supply terminal of the second circuit,a second power supply terminal, and an input/output; a first capacitorhaving a first terminal coupled to the input/output of the first circuitand a second terminal coupled to the input/output of the second circuit;and a second capacitor having a first terminal coupled to the secondterminal of the first capacitor and a second terminal coupled to theinput/output of the third circuit. The first circuit may be forprecharging the first terminal of the first capacitor to a first voltageduring a precharge phase, wherein the first voltage may be between avoltage present on the first power supply terminal and the second powersupply terminal of the first circuit. The second circuit may be forprecharging the second terminal of the first capacitor and the firstterminal of the second capacitor to a second voltage during theprecharge phase, wherein the second voltage is between a voltage presenton the first power supply terminal and the second power supply terminalof the second circuit. The third circuit may be for precharging thesecond terminal of the second capacitor to a third voltage during theprecharge phase, wherein the third voltage is between a voltage presenton the first power supply terminal and the second power supply terminalof the third circuit. The first circuit, when selected to provide anoutput, may be for providing an output signal on its input/output duringa data phase following the precharge phase. The second circuit, when thefirst circuit is selected to provide an output and the second circuit isselected to receive an input, may be for interpreting a voltage presenton the second terminal of the first capacitor in response to the firstcircuit providing the output signal to determine a logic state of theoutput signal. Each of the first, second, and third circuits may furthercomprise an identity recognition circuit for comparing an identificationportion of a received signal with a stored circuit identification valueto determine which of the first, second, and third circuits is theintended recipient of the received signal. The system may furthercomprise: a fourth circuit having a first power supply terminal coupledthe second power supply terminal of the third circuit, a second powersupply terminal, and an input/output; and a third capacitor having afirst terminal coupled to the second terminal of the second capacitorand a second terminal coupled to the input/output of the fourth circuit.The fourth circuit may be for precharging the second terminal of thethird capacitor to a fourth voltage during the precharge phase, whereinthe fourth voltage may be between a voltage present on the first powersupply terminal and the second power supply terminal of the fourthcircuit. The fourth circuit, when the first circuit is selected toprovide an output and the fourth circuit is selected to receive aninput, may be for interpreting a voltage present on the second terminalof the third capacitor in response to the first circuit providing theoutput signal to determine the logic state of the output signal. Thesystem may further comprise: a first charge pump having an input coupledto the first power supply terminal of the first circuit and an outputcoupled to the second power supply terminal of the first circuit; asecond charge pump having an input coupled to the first power supplyterminal of the second circuit and an output coupled to the second powersupply terminal of the second circuit; and a third charge pump having aninput coupled to the first power supply terminal of the third circuitand an output coupled to the second power supply terminal of the thirdcircuit. The third charge pump may pass current from the first powersupply terminal of the third circuit to the second supply terminal ofthe third circuit if a current supplied by the second circuit to thesecond power supply terminal of the second circuit exceeds a maximumcurrent requirement of the third circuit. The first charge pump mayprovide current to the second circuit if a current passing through thefirst circuit is less than a minimum current required for the secondcircuit.

In another aspect, there is provided, a method, comprising: providing afirst circuit having a first power supply terminal coupled to positivepower supply terminal, a second power supply terminal, and aninput/output; providing a second circuit having a first power supplyterminal coupled the second power supply terminal of the first circuit,a second power supply terminal, and an input/output; providing a thirdcircuit having a first power supply terminal coupled the second powersupply terminal of the second circuit, a second power supply terminal,and an input/output; providing a first capacitor having a first terminalcoupled to the input/output of the first circuit and a second terminalcoupled to the input/output of the second circuit; providing a secondcapacitor having a first terminal coupled to the second terminal of thefirst capacitor and a second terminal coupled to the input/output of thethird circuit; precharging the first terminal of the first capacitor toa first voltage during a precharge phase, wherein the first voltage isbetween a voltage present on the first power supply terminal and thesecond power supply terminal of the first circuit; precharging thesecond terminal of the first capacitor and the first terminal of thesecond capacitor to a second voltage during the precharge phase, whereinthe second voltage is between a voltage present on the first powersupply terminal and the second power supply terminal of the secondcircuit; and precharging the second terminal of the second capacitor toa third voltage during the precharge phase, wherein the third voltage isbetween a voltage present on the first power supply terminal and thesecond power supply terminal of the third circuit. The method mayfurther comprise: providing an output signal on the input/output of thefirst circuit; and interpreting a voltage present on the second terminalof the first capacitor in response to the output signal being provided.The step of interpreting may be for determining a logic state of theoutput signal. The method may further comprise interpreting a voltagepresent on the second terminal of the second capacitor in response tothe output signal being provided. The method may further comprise:passing a current through the first circuit; determining if the currentexceeds a maximum current requirement of the second circuit; if thecurrent exceeds the maximum current requirement, diverting a sufficientportion of the current away from the second circuit so that a remainingportion of the current does not exceed the maximum current requirementof the second circuit. The step of diverting is performed by passing thesufficient portion of the current through a charge pump coupled inparallel with the second circuit. The method may further comprise:passing a current through the first circuit; determining if the currentis less than a minimum current requirement of the second circuit; and ifthe current is less than the minimum current requirement, adding anadditional current to the first current so that a sum of the additionalcurrent and the first current is not less than the minimum currentrequirement of the second circuit. The step of adding may be performedby providing the additional current from a charge pump coupled inparallel with the first circuit.

In yet another aspect, there is provided, a system, comprising: aplurality of circuits having serially connected power supply terminalscoupled between a positive power supply terminal and a negative powersupply terminal; and a plurality of capacitors coupled in series;wherein: at a first end of the plurality of capacitors, a firstcapacitor has a terminal; at a second end of the plurality ofcapacitors, a last capacitor has a terminal; each circuit of theplurality of circuits has a first power supply terminal, a second powersupply terminal, and an input/output; a first circuit of the pluralityof circuits has its input/output coupled to the terminal of the firstcapacitor and is for precharging the terminal of the first capacitorduring a precharge phase to a voltage between its first and second powersupply terminals and receiving or providing data on the terminal of thefirst capacitor during a data phase following the precharge phase; alast circuit of the plurality of circuits has its input/output coupledto the terminal of the last capacitor and is for precharging theterminal of the last capacitor during a precharge phase to a voltagebetween its first and second power supply terminals and receiving orproviding data on the terminal of the last capacitor during a data phasefollowing the precharge phase; and each circuit of the plurality ofcircuits between the first and last circuits has its input/outputcoupled to a connection between two capacitors of the plurality ofcapacitors and is for precharging the connection at its input/outputduring a precharge phase to a voltage between its first and second powersupply terminals and receiving or providing data on the connection atits input/output during a data phase following the precharge phase. Thesystem may further comprise a plurality of charge pumps, wherein eachcharge pump may be coupled in parallel with one of the circuits of theplurality of circuits.

As used herein, the term “bus” is used to refer to a plurality ofsignals or conductors which may be used to transfer one or more varioustypes of information, such as data, addresses, control, or status. Theconductors as discussed herein may be illustrated or described inreference to being a single conductor, a plurality of conductors,unidirectional conductors, or bidirectional conductors. However,different embodiments may vary the implementation of the conductors. Forexample, separate unidirectional conductors may be used rather thanbidirectional conductors and vice versa. Also, plurality of conductorsmay be replaced with a single conductor that transfers multiple signalsserially or in a time multiplexed manner. Likewise, single conductorscarrying multiple signals may be separated out into various differentconductors carrying subsets of these signals. Therefore, many optionsexist for transferring signals.

The terms “assert” or “set” and “negate” (or “deassert” or “clear”) areused herein when referring to the rendering of a signal, status bit, orsimilar apparatus into its logically true or logically false state,respectively. If the logically true state is a logic level one, thelogically false state is a logic level zero. And if the logically truestate is a logic level zero, the logically false state is a logic levelone.

Each signal described herein may be designed as positive or negativelogic, where negative logic can be indicated by a bar over the signalname or an asterix (*) following the name. In the case of a negativelogic signal, the signal is active low where the logically true statecorresponds to a logic level zero. In the case of a positive logicsignal, the signal is active high where the logically true statecorresponds to a logic level one. Note that any of the signals describedherein can be designed as either negative or positive logic signals.Therefore, in alternate embodiments, those signals described as positivelogic signals may be implemented as negative logic signals, and thosesignals described as negative logic signals may be implemented aspositive logic signals.

FIG. 1 illustrates, in block diagram form, a system 10 in accordancewith an embodiment. System 10 includes a plurality of circuits such ascircuits 12, 14, and 16. Circuits 12, 14, and 16 can include any type ofcircuit, such as data processing, digital signal processing (DSP),memory, or the like. For example, circuits 12, 14, and 16 can be digitallogic circuits, analog circuits, or a combination of digital and analogcircuits. System 10 also includes a plurality of charge pump andregulator circuits, such as charge pump and regulator circuits 18, 20,and 22. The charge pump can be any kind of charge pump and the regulatorcan be any kind of voltage regulator. Circuit 12 has a first powersupply voltage terminal for receiving a power supply voltage labeled“VDD”, a second power supply voltage terminal for receiving a powersupply voltage labeled “V1”, and a plurality of bidirectional terminalsfor coupling circuit 12 to another circuit (not shown), if necessary.Circuit 14 has a first power supply voltage terminal for receiving apower supply voltage labeled “V1”, a second power supply voltageterminal for receiving a power supply voltage labeled “V2”, and aplurality of bidirectional terminals for coupling circuit 14 to anothercircuit (not shown). Circuit 16 has a first power supply voltageterminal for receiving a power supply voltage labeled “VN”, a secondpower supply voltage terminal for receiving a power supply voltagelabeled “VSS”, and a plurality of bidirectional terminals for couplingcircuit 16 to another circuit (not shown).

Each of the circuits 12, 14, through 16 belong to a “voltage tier”,where a voltage tier is determined by where it is positioned relative toother voltage tiers in the power supply voltage VDD. For example, thevoltage tier of circuit 12 is a difference between VDD and voltage V1.The voltage tier of circuit 14 is a difference between V1 and V2 and thevoltage tier of circuit 16 is voltage VN minus VSS.

Charge pump and regulator 18 has a first power supply voltage terminalfor receiving power supply voltage VDD, and a second power supplyvoltage terminal for receiving power supply voltage V1. Charge pump andregulator 20 has a first power supply voltage terminal for receivingpower supply voltage V1, and a second power supply voltage terminal forreceiving power supply voltage V2. Charge pump and regulator 22 has afirst power supply voltage terminal for receiving power supply voltageVN, and a second power supply voltage terminal for receiving VSS. Acurrent labeled “I1” can be either sourced by charge pump and regulator18, or sinked by charge pump and regulator 20. A current labeled “I2”can be either sourced by charge pump and regulator 20, or sinked by acharge pump and regulator circuit coupled to power supply voltageterminal V2 but not shown. A current labeled “I_(N)” can be eithersourced by a charge pump and regulator that is not shown, or sinked bycharge pump and regulator 22.

In one embodiment, circuits 12, 14, and 16 are implemented as CMOS(complementary metal-oxide semiconductor) logic circuits. In anotherembodiment, the circuit portions may be a different kind of logiccircuit, or an analog circuit. Also, in one embodiment, power supplyvoltage VDD is a positive power supply voltage, such as for example, 2.7volts, and VSS is at ground potential. In another embodiment, VDD may beat ground potential while VSS is a negative power supply voltage.Generally, circuit 12 has as its power supply voltage, a voltagedifference between VDD and V1 (first voltage tier). Likewise, circuit 14has a power supply voltage that is the voltage difference between V1 andV2 (second voltage tier). Also, circuit 16 has a power supply voltagethat is the voltage difference between VN and VSS (nth voltage tier).

Ideally, the power supply voltages used by each of circuits 12, 14, and16 are substantially equal. Also, a current into the VDD power supplyvoltage terminal labeled “I_(IN)” is equal to a current at the VSS powersupply voltage terminal. However, circuit differences, or imbalances,may cause one of the circuit portions to use more current than anotherone of the circuit portions. Charge pump and regulator circuits 18, 20,and 22 are used to pump a current that corrects, or compensates, for theimbalance in currents. Because the charge pump only has to provide adifference current, a relatively poor charge pump efficiency onlyapplies to the difference current and therefore minimally impacts thepower consumption. In one example, charge pump and regulator 18 suppliescurrent to circuit 14 if current supplied by circuit 12 at the powersupply node V1 is less than a minimum current requirement of circuit 14.Also, charge pump and regulator 20 passes current from voltage node V1through circuit 14 to the voltage node V2 if the current supplied bycircuit 12 to voltage node V1 exceeds a maximum current requirement ofcircuit 14. Charge pump and regulator 18 determines if the minimumcurrent requirement is met by detecting a voltage on voltage node V1.Also, charge pump and regulator 20 may determine if the maximum currentrequirement is met by detecting the voltage on the node V1. Likewise,charge pump and regulator 20 supplies current to circuit 16 (if therewere only three circuits 12, 14, and 16 in an embodiment) if the currentsupplied by circuit 14 at node V2 is less than a minimum currentrequirement of circuit 16. Charge pump and regulator 22 passes currentfrom node VN through charge pump and regulator 22 to VSS if the currentsupplied by circuit 14 to node VN (or V2) exceeds a maximum currentrequirement of circuit 16.

FIG. 2 illustrates, in block diagram form, a system 30 in accordancewith another embodiment. System 30 includes circuits 32, 34, and 36,charge pump and regulator circuit 38, 40, 42, and 44, and controlcircuit 46. Circuits 32, 34, and 36 can include any type of circuit,such as data processing, digital signal processing (DSP), memory, or thelike. For example, circuits 12, 14, and 16 can be digital logiccircuits, analog circuits, or a combination of digital and analogcircuits. Circuit 32 has a first power supply voltage terminal forreceiving a power supply voltage labeled “VDD”, and a second powersupply voltage terminal for receiving a power supply voltage labeled“V1”. Circuit 34 has a first power supply voltage terminal for receivingpower supply voltage V1, and a second power supply voltage terminal forreceiving a power supply voltage labeled “V2”. Circuit 36 has a firstpower supply voltage terminal coupled to receive a power supply voltagelabeled “V3”, and a second power supply voltage terminal for receivingpower supply voltage VSS. Each of circuits 32, 34, and 36 have aplurality of bi-directional terminals for communicating with othercircuits (not shown).

Charge pump and regulator 38 has a first power supply terminal coupledto VDD, a second power supply voltage terminal coupled to V1 for sinkingand/or sourcing a current labeled “I2”, and an input terminal forreceiving a control signal labeled “VOLTCNTL 1”. Charge pump andregulator 40 has a first power supply voltage terminal coupled to V1, asecond power supply voltage terminal coupled to V2 for sinking and/orsourcing a current labeled “I2”, and an input terminal for receiving acontrol signal labeled “VOLTCNTL 2”. Charge pump and regulator 42 has afirst power supply voltage terminal coupled to V2, a second power supplyvoltage terminal coupled to V3, and an input terminal for receivingcontrol signal VOLTCNTL 3. Charge pump and regulator 44 has a firstpower supply voltage terminal coupled to V3 for sinking and/or sourcinga current labeled “I3”, a second power supply voltage terminal coupledto VSS, and an input terminal couple to receive control signal VOLTCNTL4. Control circuit 46 has a first power supply voltage terminal coupledto receive power supply voltage VDD, a second power supply voltageterminal coupled to VSS, and output terminals for providing voltagecontrol signals VOLTCNTL 1-VOLTCNTL 4. Note that the embodiment of FIG.2 includes three circuits and four charge pump and regulator circuitsfor illustration purposes only. In other embodiments there can be anynumber of circuits, and corresponding charge pump and regulatorcircuits.

The full rail power supply voltage of system 30 is VDD, where VSS iscoupled to ground. Circuit 32 receives a power supply voltage equal toVDD minus V1, where VDD minus V1 establishes a first voltage tier.Likewise, circuit 34 receives a power supply voltage equal to V1 minusV2 (second voltage tier), and circuit 36 receives a power supply voltageequal to V3 minus VSS (third voltage tier). In one embodiment, thevoltage tiers by each of circuits 32, 34, and 36 may be intended to besubstantially equal. However, circuit imbalances may cause one of thecircuits to use more current than the other circuits. In the embodimentof FIG. 2 each of the voltage tiers can be set independently of theother tiers. Charge pump and regulator circuits 38, 40, 42, and 44 canbe used to source or sink a difference current as described above in thediscussion of FIG. 1. In addition, control circuit 46 is used to controlthe voltage drop across each of circuits 32, 34, and 36. In the eventthe supply voltage dropped by all of the circuits 32, 34, and 36 is notequal to VDD, then charge pump and regulator 42 is used to make up thedifference.

FIG. 3 illustrates, in block diagram form, a system 50 in accordancewith another embodiment. System 50 includes circuits 52, 54, and 56,input/output (I/O) circuits 58, 60, and 62, and capacitors 64 and 66.Circuit 52 has a first power supply voltage terminal coupled to receivepower supply voltage VDD, an I/O terminal, and a second power supplyvoltage terminal coupled to receive voltage V1. Circuit 54 has a firstpower supply terminal coupled to V1, an I/O terminal, and a second powersupply terminal coupled to voltage V2. Circuit 56 has a first powersupply terminal coupled to voltage V2, an I/O terminal, and a secondpower supply terminal coupled to VSS. I/O circuit 58 has a first powersupply voltage terminal coupled to VDD, a first I/O terminal forproviding or receiving data signal DQ1, a second I/O terminal coupled tothe I/O terminal of circuit 52, and a second power supply terminalcoupled to V1. I/O circuit 60 has a first power supply voltage terminalcoupled to V1, a first I/O terminal for providing or receiving datasignal DQ2, a second I/O terminal coupled to the I/O terminal of circuit54, and a second power supply terminal coupled to V2. I/O circuit 62 hasa first power supply voltage terminal coupled to V2, a first I/Oterminal for providing or receiving data signal DQ3, a second I/Oterminal coupled to the I/O terminal of circuit 56, and a second powersupply terminal coupled to VSS. Capacitor 64 has a first plate electrodecoupled to the first I/O terminal of I/O circuit 58, and a second plateelectrode coupled to the first I/O terminal of I/O circuit 54. Capacitor66 has a first plate electrode coupled to the first I/O terminal of I/Ocircuit 60, and a second plate electrode coupled to the first I/Oterminal of I/O circuit 62. Note that system 50 includes twoseries-connected capacitors for illustration purposes only. Otherembodiments may include more than two series-connected capacitors. Also,note that the described embodiment includes bi-directional I/Oterminals. In other embodiments, the I/O terminals may be implemented asseparate input and output terminals.

Circuit 52 includes circuitry for precharging the first plate electrodeof capacitor 64 to a first voltage during a precharge phase. The firstvoltage is between a voltage present on power supply terminal VDD andpower supply terminal V1 of circuit 52. Circuit 54 includes circuitryfor precharging the second plate electrode of capacitor 64 and the firstplate electrode of capacitor 66 to a second voltage during the prechargephase. The second voltage is between a voltage present on the powersupply terminal V1 and power supply terminal V2 of circuit 54. Circuit56 includes circuitry for precharging the second plate electrode ofcapacitor 66 to a third voltage during the precharge phase. The thirdvoltage is between a voltage present on power supply terminal V2 and thepower supply terminal VSS of circuit 56. Circuit 52, when selected toprovide an output signal, will provide an output signal DQ1 on its I/Oterminal during a data phase following the precharge phase. Circuit 54,when circuit 52 selected to provide an output and circuit 54 is selectedto receive an input signal DQ2, will interpret a voltage present on thesecond plate electrode of capacitor 64 in response to circuit 52providing the output signal DQ1 to determine a logic state of the outputsignal DQ1. Circuit 56, when circuit 52 is selected to provide outputDQ1 and circuit 56 is selected to receive an input DQ3, will interpret avoltage present on the second plate electrode of capacitor 66 inresponse to circuit 52 providing output signal DQ1 to determine thelogic state of output signal DQ1. Further, there can be any number ofcircuits and capacitors. For example, there may be a fourth circuit (notshown in FIG. 3) having a first power supply terminal coupled to thesecond power supply terminal of circuit 56, a second power supplyterminal coupled to VSS, and an input/output terminal coupled to anadditional capacitor. The additional capacitor having a first plateelectrode coupled to the second plate electrode of capacitor 66 and asecond plate electrode coupled to the input/output of the fourthcircuit. The fourth circuit may also include circuitry for prechargingthe second plate electrode of the third capacitor to a fourth voltageduring a precharge phase. The fourth voltage would be a fraction of thepower supply voltage between rails VDD and VSS, the magnitude of thepower supply voltage would depend on the number of voltage tiers in thesystem. The fourth circuit would communicate with circuits of the othervoltage tiers as described above.

System 50 of FIG. 3 may also include charge pump and regulator circuitsas described above for FIG. 1 and FIG. 2. For example, there may be afirst charge pump having an input coupled to the V1 terminal of circuit52, a second charge pump having an input coupled to the V1 terminal andthe V2 terminal, and a third charge pump having an input coupled to theV2 terminal. The third charge pump can pass current from the first powersupply terminal of circuit 56 to the second supply terminal of circuit56 if a current supplied by circuit 54 to the second power supplyterminal of circuit 54 exceeds a maximum current requirement of circuit56.

Series-connected capacitors 64 and 66 and I/O circuits 58, 60, and 62provide for communication between circuits of multiple voltage tiers,such as circuits 52, 54, and 56. The series-connected capacitors arefirst precharged to a predetermined voltage. The precharge voltage canbe provided by circuit 52 as illustrated in FIG. 4, or may be generatedwithin any of I/O circuits such as I/O circuit 58. The precharge voltagecauses charge to accumulate on the capacitors. Each of theseries-connected capacitors will be charged to substantially the samevoltage. Then, one of the I/O circuits provides a data bit in the formof a voltage level to the series of capacitors. The data bit can beprovided by buffer 74 as illustrated, or by another buffer (not shown).The data bit causes the voltage stored on each of capacitors 64 and 66to increase or decrease by the same amount, thereby translating the databit to each of the different voltage tiers simultaneously. For example,if the data bit is higher than the precharge voltage, the voltage levelof the capacitors is increased and a logical one may be transmitted. Ifthe data is lower than the precharge voltage, the voltage level on thecapacitors is lowered and a logic zero may be transmitted.

FIG. 4 illustrates, in block diagram form, input/output (I/O) circuit 58if system 50 of FIG. 3. I/O circuit 58 includes buffers 70 and 74, andidentity recognition circuit 72. Buffer 70 has an input terminal forreceiving signal DQ1, and an output terminal. Buffer 74 has an inputterminal coupled to receive either a precharge signal or a data signalfrom circuit 52, an output terminal for providing signal DQ1, and acontrol terminal for receiving enable signal ENABLE. Identityrecognition circuit 72 has an input terminal coupled to the outputterminal of buffer 70. Identity recognition circuit 72 is used todetermine the intended recipient of a signal transmitted to capacitors64 and 66. In one embodiment, identity recognition circuit 72 includes acomparator for comparing an identification portion of a received signalto a stored circuit identification value to determine if it is theintended recipient of the received signal. For example, an output signalDQ1 might include an identification recognition portion directing theDQ1 signal to only I/O circuit 62. I/O circuit 60 would then ignore theDQ1 signal after processing a recognition portion of the DQ1 signal.

Note that the charge pump and regulator circuits of FIGS. 1 and 2 canalso be used with the system 50 of FIG. 3.

By translating the data bit using the series of capacitors, levelshifters are not required. Also, translating using the series ofcapacitors is much faster than traditional level shifters because atraditional level shifter generally can only level shift betweenadjacent voltage tiers. To level shift a signal between multiple voltagetiers requires a level shifter between each tier and the level shiftingbetween tiers must be done serially.

Because the apparatus implementing the present invention is, for themost part, composed of electronic components and circuits known to thoseskilled in the art, circuit details will not be explained in any greaterextent than that considered necessary as illustrated above, for theunderstanding and appreciation of the underlying concepts of the presentinvention and in order not to obfuscate or distract from the teachingsof the present invention.

Although the invention has been described with respect to specificconductivity types or polarity of potentials, skilled artisansappreciated that conductivity types and polarities of potentials may bereversed.

Some of the above embodiments, as applicable, may be implemented using avariety of different information processing systems. For example,although FIG. 1 and the discussion thereof describe an exemplaryinformation processing system, this exemplary system is presented merelyto provide a useful reference in discussing various aspects of theembodiment. Of course, the description of the system has been simplifiedfor purposes of discussion, and it is just one of many different typesof appropriate systems that may be used. Those skilled in the art willrecognize that the boundaries between logic blocks are merelyillustrative and that alternative embodiments may merge logic blocks orcircuit elements or impose an alternate decomposition of functionalityupon various logic blocks or circuit elements.

Thus, it is to be understood that the systems depicted herein are merelyexemplary, and that in fact many other systems can be implemented whichachieve the same functionality. In an abstract, but still definitesense, any arrangement of components to achieve the same functionalityis effectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundariesbetween the functionality of the above described operations merelyillustrative. The functionality of multiple operations may be combinedinto a single operation, and/or the functionality of a single operationmay be distributed in additional operations. Moreover, alternativeembodiments may include multiple instances of a particular operation,and the order of operations may be altered in various other embodiments.

Although the invention is described herein with reference to specificembodiments, various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent invention. Any benefits, advantages, or solutions to problemsthat are described herein with regard to specific embodiments are notintended to be construed as a critical, required, or essential featureor element of any or all the claims.

The term “coupled,” as used herein, is not intended to be limited to adirect coupling or a mechanical coupling.

Furthermore, the terms “a” or “an,” as used herein, are defined as oneor more than one. Also, the use of introductory phrases such as “atleast one” and “one or more” in the claims should not be construed toimply that the introduction of another claim element by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim element to inventions containing only one such element,even when the same claim includes the introductory phrases “one or more”or “at least one” and indefinite articles such as “a” or “an.” The sameholds true for the use of definite articles.

Unless stated otherwise, terms such as “first” and “second” are used toarbitrarily distinguish between the elements such terms describe. Thus,these terms are not necessarily intended to indicate temporal or otherprioritization of such elements.

1. A system, comprising: a first circuit having a first power supplyterminal coupled to positive power supply terminal, a second powersupply terminal, and an input/output; a second circuit having a firstpower supply terminal coupled the second power supply terminal of thefirst circuit, a second power supply terminal, and an input/output; athird circuit having a first power supply terminal coupled the secondpower supply terminal of the second circuit, a second power supplyterminal, and an input/output; a first capacitor having a first terminalcoupled to the input/output of the first circuit and a second terminalcoupled to the input/output of the second circuit; and a secondcapacitor having a first terminal coupled to the second terminal of thefirst capacitor and a second terminal coupled to the input/output of thethird circuit, wherein the first circuit is for precharging the firstterminal of the first capacitor to a first voltage during a prechargephase, wherein the first voltage is between a voltage present on thefirst power supply terminal and the second power supply terminal of thefirst circuit; wherein the second circuit is for precharging the secondterminal of the first capacitor and the first terminal of the secondcapacitor to a second voltage during the precharge phase, wherein thesecond voltage is between a voltage present on the first power supplyterminal and the second power supply terminal of the second circuit; andwherein the third circuit is for precharging the second terminal of thesecond capacitor to a third voltage during the precharge phase, whereinthe third voltage is between a voltage present on the first power supplyterminal and the second power supply terminal of the third circuit. 2.The system of claim 1, wherein: the first circuit, when selected toprovide an output, is for providing an output signal on its input/outputduring a data phase following the precharge phase; the second circuit,when the first circuit is selected to provide an output and the secondcircuit is selected to receive an input, is for interpreting a voltagepresent on the second terminal of the first capacitor in response to thefirst circuit providing the output signal to determine a logic state ofthe output signal.
 3. The system of claim 1, wherein each of the first,second, and third circuits further comprises: an identity recognitioncircuit for comparing an identification portion of a received signalwith a stored circuit identification value to determine which of thefirst, second, and third circuits is the intended recipient of thereceived signal.
 4. The system of claim 1, further comprising: a fourthcircuit having a first power supply terminal coupled to the second powersupply terminal of the third circuit, a second power supply terminal,and an input/output; and a third capacitor having a first terminalcoupled to the second terminal of the second capacitor and a secondterminal coupled to the input/output of the fourth circuit.
 5. Thesystem of claim 4, wherein; the fourth circuit is for precharging thesecond terminal of the third capacitor to a fourth voltage during theprecharge phase, wherein the fourth voltage is between a voltage presenton the first power supply terminal and the second power supply terminalof the fourth circuit.
 6. The system of claim 5, wherein: the fourthcircuit, when the first circuit is selected to provide an output and thefourth circuit is selected to receive an input, is for interpreting avoltage present on the second terminal of the third capacitor inresponse to the first circuit providing the output signal to determinethe logic state of the output signal.
 7. The system of claim 1, furthercomprising: a first charge pump having an input coupled to the firstpower supply terminal of the first circuit and an output coupled to thesecond power supply terminal of the first circuit; a second charge pumphaving an input coupled to the first power supply terminal of the secondcircuit and an output coupled to the second power supply terminal of thesecond circuit; and a third charge pump having an input coupled to thefirst power supply terminal of the third circuit and an output coupledto the second power supply terminal of the third circuit.
 8. The systemof claim 7, wherein: the third charge pump passes a current from thefirst power supply terminal of the third circuit to the second supplyterminal of the third circuit if a current supplied by the secondcircuit to the second power supply terminal of the second circuitexceeds a maximum current requirement of the third circuit.
 9. Thesystem of claim 7, wherein: the first charge pump provides a current tothe second circuit if a current passing through the first circuit isless than a minimum current required for the second circuit.
 10. Amethod, comprising: providing a first circuit having a first powersupply terminal coupled to positive power supply terminal, a secondpower supply terminal, and an input/output; providing a second circuithaving a first power supply terminal coupled the second power supplyterminal of the first circuit, a second power supply terminal, and aninput/output; providing a third circuit having a first power supplyterminal coupled the second power supply terminal of the second circuit,a second power supply terminal, and an input/output; providing a firstcapacitor having a first terminal coupled to the input/output of thefirst circuit and a second terminal coupled to the input/output of thesecond circuit; providing a second capacitor having a first terminalcoupled to the second terminal of the first capacitor and a secondterminal coupled to the input/output of the third circuit; prechargingthe first terminal of the first capacitor to a first voltage during aprecharge phase, wherein the first voltage is between a voltage presenton the first power supply terminal and the second power supply terminalof the first circuit; precharging the second terminal of the firstcapacitor and the first terminal of the second capacitor to a secondvoltage during the precharge phase, wherein the second voltage isbetween a voltage present on the first power supply terminal and thesecond power supply terminal of the second circuit; and precharging thesecond terminal of the second capacitor to a third voltage during theprecharge phase, wherein the third voltage is between a voltage presenton the first power supply terminal and the second power supply terminalof the third circuit.
 11. The method of claim 10, further comprising:providing an output signal on the input/output of the first circuit; andinterpreting a voltage present on the second terminal of the firstcapacitor in response to the output signal being provided.
 12. Themethod of claim 11, wherein the step of interpreting is for determininga logic state of the output signal.
 13. The method of claim 12, furthercomprising interpreting a voltage present on the second terminal of thesecond capacitor in response to the output signal being provided. 14.The method of claim 11 further comprising: passing a current through thefirst circuit; determining if the current exceeds a maximum currentrequirement of the second circuit; if the current exceeds the maximumcurrent requirement, diverting a sufficient portion of the current awayfrom the second circuit so that a remaining portion of the current doesnot exceed the maximum current requirement of the second circuit. 15.The method of claim 11, wherein the step of diverting is performed bypassing the sufficient portion of the current through a charge pumpcoupled in parallel with the second circuit.
 16. The method of claim 11further comprising: passing a current through the first circuitdetermining if the current is less than a minimum current requirement ofthe second circuit; and if the current is less than the minimum currentrequirement, adding an additional current to the first current so that asum of the additional current and the first current is not less than theminimum current requirement of the second circuit.
 17. The method ofclaim 16, wherein the step of adding is performed by providing theadditional current from a charge pump coupled in parallel with the firstcircuit.
 18. A system, comprising: a plurality of circuits havingserially connected power supply terminals coupled between a positivepower supply terminal and a negative power supply terminal; and aplurality of capacitors coupled in series; wherein: at a first end ofthe plurality of capacitors, a first capacitor has a terminal; at asecond end of the plurality of capacitors, a last capacitor has aterminal; each circuit of the plurality of circuits has a first powersupply terminal, a second power supply terminal, and an input/output; afirst circuit of the plurality of circuits has its input/output coupledto the terminal of the first capacitor and is for precharging theterminal of the first capacitor during a precharge phase to a voltagebetween its first and second power supply terminals and receiving orproviding data on the terminal of the first capacitor during a dataphase following the precharge phase; a last circuit of the plurality ofcircuits has its input/output coupled to the terminal of the lastcapacitor and is for precharging the terminal of the last capacitorduring a precharge phase to a voltage between its first and second powersupply terminals and receiving or providing data on the terminal of thelast capacitor during a data phase following the precharge phase; andeach circuit of the plurality of circuits between the first and lastcircuits has its input/output coupled to a connection between twocapacitors of the plurality of capacitors and is for precharging theconnection at its input/output during a precharge phase to a voltagebetween its first and second power supply terminals and receiving orproviding data on the connection at its input/output during a data phasefollowing the precharge phase.
 19. The system of claim 18, furthercomprising: a plurality of charge pumps, wherein each charge pump iscoupled in parallel with one of the circuits of the plurality ofcircuits.